Fix incorrect position when editing the same file in 2 splits

[oxalica]

What this PR does / why we need it:
Fix setting wrong (position) states when editing the same file in two panels.

Which issue(s) this PR fixes
Fixes #3713 , hopefully.
I've checked the reproduction steps from @elprans , the test mentioned in comments, and some other random tests.
It is no longer triggered anymore.

Special notes for your reviewer:

[J-Fields]

I've got to dig into this some more, but a few things spring to mind:
This handles the same misbehavior as #3539, right? Why is this solution better?
Why don't we avoid sending the event in the first place (by modifying this conditional, say)?

[oxalica]

This handles the same misbehavior as #3539, right? Why is this solution better?

Oops, I just have not seen that. But yes, it does also fix #3455 , and not break undo.
I just keep EditorIdentity untouched. Since viewColumn can be changed, I don't know if it would cause some problems.
Well, I think EditorIdentity should be another issue.

Why don't we avoid sending the event in the first place (by modifying this conditional, say)?

You are right.

[oxalica]

Rebased to master.

[J-Fields]

Thanks for tracking this down, @uHOOCCOOHu! I'll play around with it a bit more, but this seems to work.

[kdnk]

When will this PR be released?